Information reproduction apparatus having means to control maximum delay of information being read from memory

ABSTRACT

An information reproduction apparatus capable of reducing or eliminating the mute period when a pickup jumps during the reproduction or when a disk is changed in an information reproduction system provided with a disk changer mechanism for selecting one disk from plural disks, or when a disk is forced to change, or an information reproduction apparatus of displaying the time information corresponding to the actual outputting time of information from the output terminal by correcting the time information included in the information read from the recording medium or determined by the recording address, or an information reproduction system provided with a disk changer mechanism capable of checking the contents of other disks during reproduction, or system of reproducing only parts of information to allow the monitoring of the contents of all disks.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information reproduction apparatusused in reproducing information such as digital audio signals fromdisks.

2. Description of the Related Art

Digital audio equipment utilizing optical disks has been recentlydeveloped. As a system used exclusively for reproduction, the compactdisk (referred to as CD hereafter) player is well known and, as awritable system, a write-once type is known. Further, magneto-opticaldisk systems which are capable of repeatedly recording withoutlimitation have been under development. One of such systems is a minidisk (hereinafter "MD") system disclosed in "Nikkei Electronics" (pp.160-168, Dec. 9, 1991) in an article titled "Mini disk realized throughmagneto-optical recording and data compression techniques". The MDsystem records and reproduces compressed data of audio signals onto andfrom disks by means of a magneto-optical process. A disk of this systemhas guide grooves formed thereon for tracking control, while addressinformation is recorded on the guide grooves continuously along with thecircumference of the disk. As a result, this system is capable ofsearching data regardless of whether there are signals recorded on thedisk or not.

FIG. 1 shows a block circuit diagram of the MD system. In the drawing,numeral 101 denotes 2-channel audio input terminals, numeral 102 denotesan analog/digital converter (A/D), numeral 103 denotes an encoder,numeral 104 denotes a recording signal memory, numeral 105 denotes arecording signal processing circuit which adds error correction signalsand modulates the signals, numeral 106 denotes a clock generator whichgenerates and supplies clock signals needed by various circuits of thesystem, numeral 107 denotes a recording head actuator circuit, numeral108 denotes a recording magnetic head, numeral 1 denotes a disk, numeral2 denotes an optical pickup, numeral 3 denotes a reproduction amplifier,numeral 6 denotes a reproduced signal processing circuit which carriersout demodulation and error correction, numeral 16 denotes a buffermemory, numeral 17 denotes a decoder, numeral 7 denotes a digital/analog(D/A) converter, numeral 8 denotes 2-channel audio output terminals,numeral 18 denotes an address decoder, numeral 11 denotes amicrocomputer, numeral 12 denotes a servo circuit, numeral 13 denotes adisk motor, numeral 14 denotes key input and numeral 15 denotes adisplay circuit.

FIG. 2 shows a timing chart of a prior art signal processing duringrecording and reproduction. The operation will now be described withreference to FIG. 1 and FIG. 2.

When recording, analog audio signals supplied at the audio inputterminals 101 are sampled in the A/D converter 102 and converted todigital signals. The digital audio signals are compressed and encoded inthe encoder 103 to reduce the amount of information to about one fifthof the original.

Compressed signals are temporarily stored in the recording signal memory104, and are intermittently read at the same rate as that beforecompression, as shown in FIG. 2(b). By reading the data intermittently,the difference between the rate of writing data into the memory and therate of reading data from the memory is absorbed. The recording signalprocessing circuit 105 carries out an interleaving process (wherein theorder of the signals is rearranged in order to disperse errors duringreproduction), generates and adds error correction codes and modulatesthe signals. The modulated signals are magneto-optically recorded ontothe disk 1 by the recording magnetic head 108 via the recording headactuator circuit 107. A recording operation is carried out according tothe modulation signals (FIG. 2(c)) supplied intermittently, in such amanner that signal recording action and pause are repeated alternatelyas shown in FIG. 2(d), while searching the last address of thepreviously recorded signals prior to the recording operation andrecording the signals consecutively following said last address.

When reproducing, a light beam is applied to the disk 1 by the opticalpickup 2, and the signal recorded on the disk 1 is read by means of thereflected light. The optical information is converted to electricsignals by the pickup 2 and supplied to the reproduction amplifier 3.Signals amplified by the reproduction amplifier 3 are sent to thereproduced signal processing circuit 6 where they are demodulated withsuch a method as EFM (Eight to Fourteen Modulation), processed for errordetection and error correction, subjected to an interleaving process torecover the original order of signals, and then sent to the buffermemory 16.

On the other hand, output of the reproduction amplifier 3 is suppliedalso to the address decoder 18. The address decoder 18 has the purposeof retrieving the address information included in the guide groove ofthe light spot marked in advance on the disk 1, of reproducing theaddress signals which are continuously recorded along the circumferenceof the disk and of obtaining the tracking information by detecting thewobbling of the guide grooves. The tracking information is supplied tothe servo circuit 12 wherein it is used for the purpose of trackingservo control so that the optical pickup 2 scans the specified guidegrooves and the motor 13 is servo-controlled to maintain a constantlinear velocity of the rotation of the disk 1, thereby making the guidegrooves wobble at constant frequency.

Reading of the signals from the disk 1 is carried out intermittentlysimilarly to writing of signals during recording. As shown in FIGS. 2(e)and (f), reproducing action and pause are repeated alternately, whilesignals read from the buffer memory 16 are supplied to the decoder 17and audio signals restored to the original amount of information beforecompression are converted to analog signals by the D/A converter 17 andthen sent to the audio output terminals 8. The microcomputer 11 receivesthe address signals recorded in the disk guide grooves from the addressdecoder 18 and the address signals recorded corresponding to the audiosignals, and controls the entire system upon reception of the key input14 from the outside. The microcomputer 11 also drives the displaycircuit 15 to display such information as the system operation mode andthe elapsed time during reproduction.

In this system, signals are read from the disk 1 by the optical pickup 2at a rate of about 1.4 Mbps. On the other hand, because the input rateof the decoder 17 is about 0.3 Mbps, the buffer memory 16 becomes fullof data when signals are read from the disk for about 0.9 seconds ifbuffer memory 16 of 1M bits is used. Compressed data stored in thebuffer memory 16 to the full capacity thereof sustains reproduction forabout 3 seconds.

Thus even when the optical pickup 2 jumps due to an externaldisturbance, for example, it does not immediately cause interruption ofsound reproduction because the buffer memory 16 holds the data.Accordingly, continuous reproduction without interruption can be carriedout by searching the signals at the location immediately before the jumpand writing the signals in the buffer memory 16 before the signalsstored in the buffer memory 16 are consumed.

However, in the case that the pickup 2 comes off the track due to animpact while a small amount of data remains in the buffer memory 16during reproduction, the data in the buffer memory 16 may be used up andthe sound reproduction may be interrupted.

Further, because the data is delayed by being stored in the buffermemory 16, display of the address or time information reproduced by thepickup 2 becomes different from that corresponding to the outputtingdata from the terminals 8.

As an information reproduction apparatus to select one of a plurality ofdisks loaded on the apparatus and reproduce it, there is an onboard orstand-alone CD player equipped with a magazine-type disk changer. FIG. 3shows a block circuit diagram of a conventional CD player equipped witha magazine-type disk changer. In the drawing, numeral 4 denotes ademodulation circuit, numeral 5 denotes a signal processing circuit,numeral 9 denotes a digital output circuit, numeral 10 denotes a digitalaudio output terminal and numeral 100 denotes a changing mechanism. Sixto ten CD's are loaded on a magazine which is mounted on the changingmechanism 100 of the player. A CD specified by the user is picked out ofthe magazine and loaded on the disk mechanism (not shown in the drawing)and reproduced. Therefore, if the user makes a key operation for diskchange to reproduce another disk when a disk is being reproduced, firstthe rotation of the disk currently reproduced is stopped and the disk isstored in the magazine, then another disk which has been specified istaken out of the magazine, loaded on the disk mechanism and is rotatedto start the reproduction.

Changing a disk in an information reproduction apparatus equipped withsuch a changer system requires much time since operation as will bedescribed below must be done after the reproduction of one disk iscompleted and before the next disk is reproduced.

1. Stop the disk rotation.

2. Store the disk which has been reproduced in the magazine.

3. Take out the disk to be reproduced next from the magazine.

4. Load the disk.

5. Rotate the disk.

6. Read the TOC (Table of Contents) information.

Also since a CD usually includes a mute portion equivalent to two tothree seconds following the end of the program, it takes about two orthree seconds before starting the above operations after the program iscompleted, making the mute period during disk change longer.

As described above, because changing of the disk takes at least severalseconds during which a mute state without reproduced sound continues,attempts have been made to increase the speed of the disk changingmechanism and reduce the mute period, but there has been a limitation tothese attempts. An attempt to eliminate the mute period by utilizing amemory is disclosed in an unexamined Japanese Laid-Open PatentApplication No. H3-273586. In this apparatus, signals are read from a CDat a rate higher than the reproduction speed and stored in the memoryfrom which signals are read at the specified reproduction rate. Duringthe mute period of disk change reading of signals stored in the memoryis continued, thereby substantially eliminating the mute period.

In such an apparatus, a mute period can be eliminated or reduced when aplurality of Cd's are reproduced in the predetermined order and in thepredetermined order of music pieces in each CD, although it has noeffect of reducing the mute period in case the user forcibly commandsdisk change during reproduction because the necessary signals are notstored in the memory.

SUMMARY OF THE INVENTION

The present invention has been conceived in order to solve the problemsdescribed above. A first object of the invention is to provide aninformation reproduction apparatus capable of reducing or eliminatingthe mute period when the pickup jumps during reproduction, when changingthe disk in the information reproduction system equipped with a diskchanger mechanism which selects one disk from a plurality of disks andreproduces information from the selected disk, or when the disk ischanged forcibly.

A second object of the invention is to provide an informationreproduction apparatus capable of displaying the time informationdetermined by the time information included in the reproducedinformation or determined by the address, by correcting the informationand obtaining time information which corresponds to the actual outputtime when the information is provided at the output terminal.

A third object of the invention is to provide an informationreproduction apparatus capable of checking the contents of other disksduring reproduction of a disk in an information reproduction systemequipped with a disk changer mechanism which selects one disk from aplurality of disks and reproduces information from the selected disk, orto provide an information reproduction apparatus capable of checking thecontents of disks and collectively reproducing part of informationthereof.

The above and further objects and features of the invention will morefully be apparent from the following detailed description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block circuit diagram of a conventional MD system;

FIG. 2(a) shows a timing chart of an input to an encoder of theconventional MD system;

FIG. 2(b) shows a timing chart of an output of a recording signal memoryof the conventional MD system;

FIG. 2(c) shows a timing chart of output of a recording signalprocessing circuit of the conventional MD system;

FIG. 2(d) shows a timing chart of the recording status of theconventional MD system;

FIG. 2(e) shows a timing chart of the reproduction status of theconventional MD system;

FIG. 2(f) shows a timing chart of reproduced signal of the conventionalMD system;

FIG. 2(g) shows a timing chart of input to a buffer memory of theconventional MD system;

FIG. 3 shows a block circuit diagram of a CD player equipped withmagazine-type disk changer of the prior art;

FIG. 4 shows a block circuit diagram of Embodiment 1 of the informationreproduction apparatus of the invention;

FIG. 5(a) is a schematic drawing of data storage in the buffer memory ofEmbodiment 1;

FIG. 5(b) is a schematic drawing of data storage in the buffer memory ofEmbodiment 1;

FIG. 6(a) shows a graph illustrative of the change in the amount of datawhen large values are set for the amount of data stored in the buffermemory and reference value E in Embodiment 1;

FIG. 6(b) shows a graph illustrative of the change in the amount of datawhen small values are set for the amount of data stored in the buffermemory and reference value E in Embodiment 1.

FIG. 7 shows a block circuit diagram of write flag generation circuit ofEmbodiment 1;

FIG. 8 shows a block circuit diagram of Embodiment 2 of the informationreproduction apparatus of the invention;

FIG. 9 shows a block circuit diagram of Embodiment 3 of the informationreproduction apparatus of the invention;

FIG. 10 shows a block circuit diagram of Embodiment 4 of the informationreproduction apparatus of the invention;

FIG. 11(a) shows a graph illustrative of the change in reproduced signallevel with time;

FIG. 11(b) shows a timing chart of disk rotation and pause in theinformation reproduction apparatus of the prior art;

FIG. 11(c) shows a timing chart of disk rotation and pause in theinformation reproduction apparatus of Embodiment 4;

FIG. 12 shows a block circuit diagram of Embodiment 5 of the informationreproduction apparatus of the invention;

FIG. 13(a) shows a timing chart of writing data in buffer memory of theinformation reproduction apparatus of Embodiment 5;

FIG. 13(b) shows a timing chart of output data from the decoder of theinformation reproduction apparatus of Embodiment 5;

FIG. 14(a) shows a timing chart of reproduction output in the CD systemof the prior art;

FIG. 14(b) shows a timing chart of reading data from disk in Embodiment2;

FIG. 14(c) shows a timing chart of reproduction output in Embodiment 2;

FIG. 14(d) shows a timing chart of reading data from disk in Embodiment5;

FIG. 14(e) shows a timing chart of reproduction output in Embodiment 5;

FIG. 15 shows a block circuit diagram of Embodiments 6 and 7 of theinformation reproduction apparatus of the invention;

FIG. 16(a) shows a graph illustrative of the change in reproduced signallevel with time of a CD system of the prior art.

FIG. 16(b) shows a timing chart of a reproduction output in the CDsystem of the prior art;

FIG. 16(c) shows a timing chart of reading data from a disk inEmbodiment 6;

FIG. 16(d) shows a timing chart of a reproduction output in Embodiment6;

FIG. 16(e) shows a timing chart of a reproduction output in Embodiment7;

FIG. 17 is an approximate drawing illustrative of the output wheninterrupting the reproduction in the information reproduction apparatusof Embodiments 4 through 7;

FIG. 18 shows a block circuit diagram of Embodiment 8 of the informationreproduction apparatus of the invention;

FIG. 19 shows a schematic diagram of the second memory of theinformation reproduction apparatus of Embodiments 8 and 9 of theinvention.

FIG. 20 shows a flow chart of the operation of the informationreproduction apparatus of Embodiment 8;

FIG. 21 shows a flow chart of the operation in Embodiment 9 of theinformation reproduction apparatus of the invention; and

FIG. 22 shows a block circuit diagram of Embodiment 10 of theinformation reproduction apparatus of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

The information reproduction apparatus of the invention will now bedescribed below with reference to the attached drawings. Portionsidentical or equivalent to those in the prior art are assigned identicalnumerals and will not be explained. FIG. 4 shows a block circuit diagramof Embodiment 4, wherein the recording section is omitted and with onlythe reproduction section being indicated. In the drawing, numeral 16denotes a buffer memory, numeral 31 denotes a circuit generating theaddress of writing in buffer memory 16, numeral 32 denotes a circuitgenerating the address of reading data from buffer memory 16, numeral 33denotes a selector, numeral 34 denotes a write flag generator circuitwherein a write flag is generated from the difference between the readaddress 32a and write address 31a and the reference value received on aninput terminal 36. Numeral 35 denotes a write control circuit whichcontrols writing into the buffer memory 16 by regulating the clocksignal supplied to the write address generator circuit 31 and the writepulse 35a to the memory 16.

FIG. 5 shows a memory map illustrative of the relationship between theamount of data stored in the buffer memory having an m-bit address andthe write and read addresses, wherein W denotes data being written and Rdenotes data being read. The write address and the read address changecyclically from 0 to 2^(m-1) (where 2^(m) is the capacity of the buffermemory) while counting up. FIG. 5(a) shows a case wherein the writeaddress is greater than the read address, with the hatched portionindicating the amount of data stored in the memory 16 and showing thatthe larger the area of the hatched portion is, the longer the time ofoutputting data from memory 16 after stopping the writing operationbecomes. FIG. 5(b) shows a case wherein the address has increased overthat in FIG. 5(a), with the address of W returning to 0 and the addressof R has become greater than W by counting up further.

The operation of the invention will be described below. Data with errorsbeing corrected in the reproduced signal processing circuit 6 isintermittently written in the buffer memory 16 according to the writeaddress generated in the write address generation circuit 31. Thewriting operation is carried out at a rate of 1.4 Mbps. On the otherhand, data stored in the buffer memory 16 is continuously read at a rateof 0.3 Mbps according to the address generated in the read addressgeneration circuit 32. The write flag generation circuit 34 calculatesthe amount of data remaining in the buffer memory 16 from the differencebetween the write address 31a and the read address 32a and, when thecalculated amount of data is below the first reference value E which hasbeen input from the terminal 36, sets the write flag to 0 (write enable)and, when the calculated amount of data is greater than the maximumvalue of address 2^(m) or greater than the second reference value Fwhich has been selected in advance from values less than 2^(m) -1 in thevicinity of 2^(m) -1, sets the write flag to 1 (write disable).

The write control circuit 35 controls the write address generationcircuit 31 to generate an address for writing the data reproduced fromthe disk 1 in the memory 16 and sends a write pulse 35a to the buffermemory 16 when the write flag is 0. When the write flag is 1, the writecontrol circuit 35 stops the supply of clock signals to the writeaddress generation circuit 31 to prevent the write address from beingupdated and stops the supply of write clock signals to the memory 16.

Thus, data is written in the memory 16 when the amount of data stored inthe buffer memory 16 decreases below the first reference value E, andwriting is disabled until the amount of data in the memory 16 decreasesto the level E when the amount of data stored in the buffer memory 16increases up to the second reference value F which indicates the amountof data in the buffer memory 16 near overflow.

FIG. 6 shows graphs illustrative of the changes in the amount of datastored in the buffer memory 16, wherein time is plotted as an abscissaand the amount of data in the buffer memory 16 is plotted as anordinate. FIG. 6(a) shows a case of setting a large value for the firstreference value E and FIG. 6(b) shows a case of setting a small valuefor the first reference value E. Setting as shown in FIG. 6(a) isadvantageous in countering vibration because a sufficient amount of datais always stored in the memory 16. Setting as shown in FIG. 6(b)provides long write-disabled periods and enables one to utilize thewrite-disabled periods in reproduction for other tasks. The firstreference value E is determined by using the terminals 36 in accordanceto the application.

In case the optical pickup 2 comes off track, the address decoder 18detects the deviation and sends a signal to notify the deviation to thewrite control circuit 35. In case of an off-track error, the writecontrol circuit 35 disables writing until a normal address is restored,even when the amount of data in the memory 16 decreases below E.

FIG. 7 shows a block circuit diagram illustrative of an example of theconstruction of the write flag generation circuit 34. Numeral 40 denotesa subtracter which subtracts the value of read address 32a from thevalue of write address 31a. Numeral 41 denotes a polarity judgmentcircuit which senses the polarity of output from the subtracter 40 andprovides an output of 0 when the polarity is plus, or provides an outputof 2^(m) when the polarity is minus. Numeral 42 denotes an adder.Numeral 43 denotes a comparator which determines whether the output fromthe adder 42 is greater or less than the reference value. The subtracter40, the polarity judgment circuit 41 and the adder 42 constitute anarithmetic unit 44 which calculates the amount of data remaining in thebuffer memory 16.

In the case of FIG. 5(a), output of the adder 42 is the same as theoutput of the subtracter 40 because the output of the subtracter 40 ispositive. In the case of FIG. 5(b), the adder 42 adds 2^(m) to the valueof subtracter 40 and provides it as the output because the output of thesubtracter 40 is negative. Data remaining in the memory portionindicated by the hatched area in FIG. 5 is thus taken out as positivevalues by the polarity judgment circuit 41. The comparator 43 gives anoutput of 1 when the output of the adder 42 is less than the firstreference value E, and gives an output of 0 when the second referencevalue F (which is set near the maximum memory capacity 2^(m)) is reachedto prevent overflow of the memory 16, so that the write control circuit35 disables writing.

Embodiment 2

FIG. 8 shows a block circuit diagram illustrative of Embodiment 2 of theinformation reproduction apparatus of the invention. In FIG. 8, numeral50 denotes a sub data extraction circuit which extracts informationrepresenting the position on the disk or the time informationrepresenting the elapsed reproduction time from the reproduced signals.This embodiment relates to a system equipped with a magazine-type diskchanger which accommodates a plurality of disks 1 capable ofcontinuously reproducing all disks or reproducing selected programs.While the disk changer system continues the reproduction byautomatically replacing the disk which has been completed with the nextdisk, this disk changing operation results in a mute period of 10 to 15seconds.

When a RAM with a capacity of 1M bits is used for the buffer memory 16,compressed signals equivalent to 3 seconds in terms of reproduction timecan be stored in case of an MD system, and therefore compressed signalsequivalent to 12 seconds can be stored in a memory of 4M bits.Embodiment 2 reduces the mute period during disk change by utilizingthis capability.

Now the operation will be described below.

Continuous reproduction or programmed reproduction is selected by keyinput 14 and, in the case of programmed reproduction, disk No. andchannel No. of the music piece to be reproduced are also designated.Data of these designations is stored in the internal memory (not shown)of the microcomputer 11 which determines whether the last music piece tobe reproduced in the disk currently reproduced has been completed or notbased on the address indicating the position on the disk or the timeinformation extracted by the sub-information extraction circuit 50. Thelast piece of music refers to the piece of music at the end of a disk inthe case of continuous reproduction or the music piece programmed at theend of the programmed sequence of the music pieces of the disk in thecase of programmed reproduction. Start position, end position and timeinformation of each music piece can be obtained by reading the TOC(Table of Contents) recorded in a portion of the disk.

The microcomputer 11, when it determines that a music piece iscompleted, turns the write stop signal 11b to stop mode and sends it tothe write control circuit 35 to prohibit writing of reproduced signalsin the memory 16. When writing is prohibited, write address is notupdated and write clock signals to the memory 16 are not supplied.

Then when the disk 1 is changed and demodulated signals are normallyreproduced, demodulation OK signal 6a is delivered from the reproducedsignal processing circuit 6. The microcomputer 11, when it detects thissignal, turns the write stop signal 11b to the release mode. The writecontrol circuit 35 writes the music pieces of the new disk 1 in thebuffer memory 16 while updating the address, so that the last musicpiece of the previous disk 1 and the first music piece of the new disk 1are stored in the buffer memory 16 substantially adjacent one another,thereby reducing the mute period during disk change.

The length of time absorbed by the delay of the output with respect tothe input to the buffer memory 16 can be freely selected by changing thecapacity 2^(m) of the buffer memory 16. However, if a memory ofexcessively large capacity is used, length of time being absorbedbecomes too long to cause sound to be produced even after thereproduction is stopped in case only one disk is reproduced, resultingin an unnatural feeling. Therefore, when a memory of large capacity isused, it is preferable to store a large amount of data in the memory 16by setting a value of the first reference E as shown in FIG. 6(a) onlywhen the system is programmed to reproduce the next disk. When listeningto the sound with the system being placed in another room, the firstreference value E may be set always at a high level.

Embodiment 3

FIG. 9 shows a block circuit diagram of Embodiment 3 of the informationreproduction apparatus of the invention. Numeral 51 denotes a registerused to hold the output from the address decoder 18. Numeral 52 denotesan address conversion circuit which corrects the output from theregister 51 by using the output from the arithmetic unit 44 (see FIG. 7)which constitutes the write flag generation circuitry 34.

As described so far, delay time in the buffer memory 16 increases aslarger capacity is used for the buffer memory 16. Consequently whenaddress data extracted by the address decoder 18 is converted to timedata by the microcomputer 11 and is displayed, disparity between themusic piece provided at the output terminal 17 and the time informationincreases. For example, when up to 12 seconds of delay is caused with amemory of 4M bits being used, output of the second music piece begins tobe given at the terminal 8 at the time when the display shows that 12seconds have passed after the program has changed to the second musicpiece.

This embodiment eliminates such inconveniences. The register 51 latchesthe address provided by the address decoder 18. While the value of theregister 51 is updated during writing into the buffer memory 16, it isnot updated when writing is disabled. Therefore the address held by theregister 51 is the latest of data which has been written in the buffermemory 16, and can be said to correspond to the position information ofthe data stored at the address designated by the write address.

On the other hand, output from the arithmetic unit 44 of the write flaggeneration circuit 34 is the difference between the read address and thewrite address. This data is converted by the address conversion circuit52 to the difference of address on disk 1. This conversion can becalculated easily because the amount of data included in one address isconstant. Then the address conversion circuit 52 subtracts the addressdifference obtained form the address held by the register 51 and sendsthe result to the microcomputer 11, which converts the data to time anddisplays it. Because the address provided by the address conversioncircuit 52 corresponds to the address of the data read from the buffermemory 16, there occurs no disparity between the actual elapsed time ofreproduction of the current music piece and the displayed time.

Delay time in the reproduced signal processing circuit 6 and in thedecoder 17 is usually negligible, and therefore correction of only thedelay time in the buffer memory 16 may suffice. When time information isto be obtained from the address reproduced from the disk 1, themicrocomputer 11 converts it to time information and displays it.

While output from the sub data extraction circuit 50 is used indetermining the end of a music piece in Embodiment 2, similar effect canbe obtained by using the output from the address decoder 18.

While output from the address decoder 18 is used to correct the addressin Embodiment 3, a similar effect can be obtained by installing the subinformation extraction circuit 50 of FIG. 8 and using the outputtherefrom.

While the second reference F is fixed in the above embodiments, such anarrangement that allows one to freely set the second reference value Fsimilarly to to the first reference value E may also be employed.

While examples are given for audio signals in the above embodiments,similar effects can be obtained with an apparatus for reproducingdigital signals.

Embodiment 4

FIG. 10 is a drawing illustrative of the construction of Embodiment 4 ofthe information reproduction apparatus according to the invention. InFIG. 10, numerals 1 through 5 and 7 through 15 denote componentsidentical with those of the prior art shown in FIG. 3, and thereforedescription thereof will be omitted. Numeral 20 denotes an end detectioncircuit which detects the end of program stored in a disk currentlybeing reproduced.

In this embodiment, time series of digital audio signals restored intothe original signals by the signal processing circuit 5 are supplied tothe end detection circuit 20. The end detection circuit 20 determinesthat the program has come to its end when the reproduced signal leveldecreases below the specified level before the end time of the programon a disk.

FIG. 11 shows a timing chart when the end of a program is detected. FIG.11(a) shows the reproduced signal level, FIG. 11(b) shows the operationmode of a CD system of the prior art and FIG. 11(c) shows the operationmode of Embodiment 4.

It is already known from the reproduction time of a music piece recordedin the TOC information of a CD that the program will end at time t3, anda CD system of the prior art ends the reproduction of the program attime t3 stopping the disk 1 at this time. However, in an embodiment ofthe invention, the end detection circuit 20 monitors the reproducedsignal level during a specified period of q seconds before the programend time t3 and, in case no sound is produced or signals below thethreshold level continue for the specified period of p seconds (p<q), itis determined that no sound will be produced in the remaining periodfrom t2 to t3 and reading from the disk 1 is interrupted at t2,thereupon rotation of the disk 1 is immediately stopped.

With such a scheme as described above, it is made possible to reduce thetime before stopping the disk 1 by s seconds. If this scheme is appliedto a system which automatically changes a plurality of disks, the periodwithout sound (i.e. mute period) during disk change can be reduced andtherefore the period of time before starting the reproduction of thenext disk after ending the reproduction of the present disk can bereduced.

Embodiment 5

Embodiment 5 further reduces the mute period during disk change byutilizing buffer memory of an MD system which temporarily storescompressed information which has been reproduced in the buffer memoryand outputs it after decoding thereof.

FIG. 12 shows the construction of this embodiment. In FIG. 12,components identical with or equivalent to those previously illustratedare assigned the same numerals as previously and description thereofwill be omitted.

Now the operation will be described below. Processes for reading of thesignals written on the disk 1 by means of the pickup 2, error correctionfor the train of signals in the signal processing circuit 5 to thede-interleaving process (wherein the train of signals the order of whichwas rearranged in the interleaving process is returned to the originalorder) are the same as those in the prior art. The buffer memory 16 andthe decoder 17 are used to temporarily store input data suppliedintermittently, to decode the compressed data and to continuouslyprovide the output of the original time series data, under the controlof the microcomputer 11 as shown in FIG. 13. Namely, a train of signalsentered in the memory 16 during the period from to t1 in FIG. 13 iscontinuously outputted in the period from time t2 to t4. Similarly,trains of signals entered during periods from t2 to t3, from t4 to t5and from t6 to t7 are continuously provided as outputs during periodsfrom t4 to t6, from t6 to t8 and from t8 to t10. Periods from t1 to t2,from t5 to t6 and from t7 to t8 (hatched portions in the drawing) areperiods wherein writing in the buffer memory 16 is disabled.

Signals restored into the original continuous time series, as describedabove, pass to the D/A converter 7 to be provided at the analog audiooutput terminal 8 as analog audio signals, while at the same time theypass to the digital output circuit 9 to be provided at the digital audiooutput terminal 10 as digital audio signals in conformity with thedigital audio interface standard. The microcomputer 11 carries outvarious control tasks over the servo circuit 12, signal processingcircuit 5, etc. based on the reproduced additional information and thekey input 14, while at the same time displaying information such as thesystem operation mode and time on the display section 15.

In this embodiment, the mute period is further made shorter than that inEmbodiment 2, while the disk stops before the reproduced signals endwith the use of the buffer memory 16 as in Embodiment 2. FIGS. 14(a)-(e)show a timing chart at the end of the program. FIG. 14(a) shows thereproduction output of a CD of the prior art, FIG. 14(b) shows the diskreading timing in Embodiment 2, FIG. 14(c) shows the reproduction outputin Embodiment 2, FIG. 14(d) shows the disk reading timing in Embodiment5 and FIG. 14(e) shows the reproduction output in Embodiment 5.

In the CD system of the prior art, reproduction of the program isfinished at time t5 whereupon rotation of the disk is stopped and thedisk is changed, then reproduction of the next disk is started at timet11, as shown in FIG. 14(a). Therefore, no sound is produced during aperiod of k seconds which is taken to change the disk. In Embodiment 2where the buffer memory 16 is used, however, reading from the disk 1 isfinished at time t3, whereupon rotation of the disk 1 is stopped anddisk change is started. Then, reading from the next disk 1 is started attime t6 under the control of the microcomputer 11, as shown in FIGS.14(b) and (c). In this case, because the reproduced signals aretemporarily stored in the buffer memory 16, reproduction output of thecontinuous time series is continued until time t5 and reproductionoutput is restarted at time t9. Thus, the period without sound in thisembodiment is reduced by h seconds to become k-h seconds, assuming thatthe time taken in disk change remains to be k seconds.

Further, in Embodiment 5, an operation as described below is madepossible. In this embodiment, when restarting reproduction of the disk1, it is controlled by the microcomputer 11 so that data which has beenread from the disk 1 first is immediately decoded and is outputted, andthe second and the following reading operations are carried out as shownin FIGS. 14(d) and (e), wherein the second and following readingoperations are similar to the prior art. Then, in this case, the periodwithout sound is further made shorter by i seconds than that inEmbodiment 2. That is, as sown in FIGS. 14(d) and (e), data which hasbeen read from the disk 1 in the period from time t6 to t7 isimmediately decoded and is outputted in the period from t7 to t10, anddata read in the period from time t7 to t8 is outputted after time t10.By this operation, the period without sound is further reduced by iseconds to k-h-i seconds. The hatched portion in FIG. 14 represents theperiod without sound.

Embodiment 6

FIG. 15 shows a block circuit diagram of Embodiment 6 of the informationreproduction apparatus of the invention. Components identical with orequivalent to those of the prior art or previous embodiments areassigned the same numerals as previously, and description thereof willbe omitted. In this embodiment, end detection circuit 20 similar to thatof Embodiment 4 is added to the MD system which employs a buffer memoryto temporarily store compressed data.

Time series of digital audio signals restored into the original signalsin the signal processing circuit 5 are fed to the end detection circuit20. When the reproduced signal level decreases below the specified levelwithin the end time of the program of one disk, the end detectioncircuit 20 determines that the program has come to an end.

FIGS. 16(a)-16(e) show a timing chart when the end of the program isdetected. In the drawing, FIG. 16(a) shows the reproduced signal level,FIG. 16(b) shows the reproduced output of DC of the prior art, FIG.16(c) shows the timing of the reading disk in Embodiment 6, FIG. 16(d)shows the reproduction output of Embodiment 6 and FIG. 16(e) shows thereproduction output of Embodiment 7.

It is already known from the reproduction time of a music piece recordedin the TOC information of a CD that the program will end at time t6, anda CD system of the prior art ends the reproduction of the program attime t6 stopping the disk 1 at this time, changing the disk, and then,starting the reproduction of the next disk at time t11. As a result, nosound is produced for the k seconds which are taken in changing the disk(hatched portion Y), and signals with no sound or a very low soundlevel, below the audible limit at the end of a program, are reproducedfor h seconds (hatched portion X), resulting in a mute period of h+kseconds.

However in this embodiment, which employs the buffer memory 16 and theend detection circuit 20, the reproduced signal level during a specifiedperiod of q seconds before the program end time t6 is monitored and, incase no sound is produced or signals below the threshold level continuefor the specified period of p seconds (p<q), namely from time t3 to t4,it is determined that no sound will be produced also in the remainingperiod from t4 to t6 and thereby reading of compressed signals from thedisk 1 is interrupted at t2, thereupon rotation of the disk 1 isimmediately stopped and disk change is started to restart reading fromthe next disk 1 at time t7. In this case, because the reproduced signalsare temporarily stored in the buffer memory 16, reproduction output ofthe continuous time series is continued until time t5 and reproductionoutput is restarted at time t9, thus the period without sound in thisembodiment is reduced by i seconds to become k+h-i seconds (assumingthat the time taken in disk change remains as k seconds). In FIGS.16(b), 16(d) and 16(e), hatched portion X represents reproduction outputwhich can be regarded as soundless, and the hatched portion Y representsa portion where soundless signals are reproduced due to disk change orthe like.

Embodiment 7

Further, as shown in FIG. 16(e), when restarting reproduction of thedisk 1, if data which has been read from the disk 1 first is immediatelydecoded and is outputted, and the second and the following readingoperations are carried out similarly to the prior art, then the periodwithout sound is further made shorter by j seconds to become h+k-i-jseconds.

While a reproduced signal level is used in the detection of signalswithout sound or with low-level audio signals in Embodiments 4 through7, such signals may be judged by using, for example, a valuerepresenting the range of the reproduced signals such as scale factor.

Also, while the operation of reading from the disk 1 is interrupted whenthe reproduced signals become mute or below the audible limit inEmbodiments 4 through 7, the threshold may be selected to set a desiredlevel and, in this case, information that follows the interruption ofreading from the disk 1 may be processed to obtain approximatereproduction signals for output so that noise is not generated as shownin FIG. 17.

FIG. 18 shows a block circuit diagram of Embodiment 8 of the informationreproduction apparatus of the invention. In the drawing, componentspreviously illustrated are assigned the same numerals as previouslyassigned, and thus, the description thereof will be omitted.

In the drawing, numeral 19 denotes a low-pass filter (LPF), numeral 21denotes an error correction circuit, numeral 22 denotes a memory datainput circuit, numeral 23 denotes a first memory, numeral 24 denotes anaddress control circuit for the first memory, numeral 25 denotes asecond memory and numeral 26 denotes an address control circuit for thesecond memory.

Similar to the prior art, reproduced signals demodulated by thedemodulator 4 are fed to the error correction circuit 21 for errordetection and correction, then subjected to a deinterleave process torestore the order of interleaved signals into the original order.Regenerated signals which have passed this process are written into thefirst memory 23 under the control of the address control circuit 24 viathe memory data input/output circuit 22. Regenerated signals which havebeen once stored in the memory 23 are read and supplied to the decoder17 via the memory data input/output circuit 22.

Writing of signals into the first memory 23 is done at a rate fasterthan that of reading from the first memory 23. That is, signals of thedisk 1 are read faster than the transfer speed of the output from thefirst memory 23, and consequently, the amount of signals stored in thememory 23 increases. When the amount of signals stored in the memory 23exceeds a specified level (overflow point) which has been set inadvance, the memory data input/output circuit 22 stops the writing ofsignals in the memory 23. At the same time, the microcomputer 11memorizes the position on the disk at this time and controls the servocontrol circuit 12 to repeat searching of the position. While this isdone, reading of signals from the first memory 23 is continued at aconstant rate and, when the amount of signals stored in the memoryreaches a specified level (underflow point) which has been set inadvance, the memory data input/output circuit 22 causes the writing ofsignals to be restarted. Thus, signals of amounts at least not less thanthe underflow point are maintained in the first memory 23. Therefore,even when the optical pickup 2 jumps to become unable to follow thespecified track due to external disturbance so that writing of signalsinto the first memory 23 is disabled, reading of signals which have beenstored is continued during which the reproduction point before thepickup jumped is searched and the optical pickup 2 is restored to thereproduction point, thereby enabling continued output from the firstmemory 23.

When disks are loaded on this information reproduction apparatus, themicrocomputer 11 directs the disk changer mechanism 100 to automaticallytake out each of the disks from five disks successively, one at a time,and load it on the disk mechanism. Although the loaded disk 1 isreproduced similarly to the ordinary reproduction, what is reproduced isthe specified period at the start of the first music piece, for example10 seconds. While signals which are read by the optical pickup 2 at thistime are sent through the signal path described above to the memoryinput/output circuit 22, they are stored in the second memory 25, not inthe first memory 23. FIG. 19 shows a schematic diagram illustrative ofthe data stored in the second memory 25. Compressed signals of the first10 seconds of the first music piece of each disk are stored in the areas1 through 5 of the second memory 25. Correspondence between the disknumbers and the areas of the memory is controlled by the microcomputer11.

Now the operation in case the user selects disk change during thereproduction of a disk will be described hereinbelow.

FIG. 20 shows a control flow chart explanatory of the operation in thiscase. First, when a disk change command is entered by key input 14 (S1),the microcomputer 11 mutes the audio output form the disk beingreproduced (S2) while at the same time stopping the disk rotation andcommanding the changer mechanism 100 to change the disk, thereby tostart disk change (S3). Then the microcomputer 11 commands the memoryaddress control circuit 26 to read signals from the second memory 25,which correspond to the disk to be reproduced next, as designated by keyinput 14. The address control circuit 26 carries out the specifiedaddress control operation to select the signals of the first 10 secondsof the first music piece of the specified disk and reads the signals(S4). At this time, the memory data input/output circuit 22 selects thesignals in order to send the signals read from the second memory 25, notfrom the first memory 23, to the decoder 17. The muting is cancelled(S5), and signals restored by the decoder 17 are outputted via D/Aconverter 7 and the LPF 19 at the audio output terminals 8, and throughthe digital output circuit 9 at the digital audio output terminals 10.

At this time, because the signals outputted form the second memory 25are compressed audio signals corresponding to a period of 10 seconds,audio signals of the first 10 seconds of the first music piece can bereproduced. During this period, the changer mechanism 100 changes thedisk and, when the disk to be reproduced is loaded, a signal positionthat follows the audio signals of the first 10 seconds of the firstmusic piece is searched at a high speed (S6). That is, because thesignals stored on the disk are provided with the address informationrecorded at the specified intervals, the microcomputer 11 memorizes thelast address of the signals which have been input to the memory 25, andsearches the next address that follows said address.

Then the optical pickup 2 reads the signals starting at the searchedposition, with the signals being stored in the first memory 23 similarlyto the stationary reproduction operation described above (S7). Alsooutputted in this period are the signals stored in the second memory 25.After the last signal in the second memory 25 is outputted (S8), thememory input/output circuit 22 is switched to output the signals fromthe first memory 23 (S9), and the memory address control circuit 24controls the memory address to successively read out the signals fromthe memory. Consequently, signals which have been stored in the memory25 in advance are reproduced in the first 10 seconds, and signals readfrom the disk which follow the first 10 seconds can be reproducedwithout discontinuity.

Embodiment 9

FIG. 21 shows a flow chart illustrative of the operation of the MDchanger system. Block construction of the system is similar to thatshown in FIG. 18. When disks are loaded, compressed signals of the first10 seconds of the first music piece of each disk are stored in the areas1 through 5 of the second memory 25, as described previously.

When the user wants to check the contents of another disk duringreproduction of a disk, the user operates the corresponding key (S11)upon which the microcomputer 11 controls the system to read the signalsfrom the corresponding area of the second memory 25. That is, for thememory data input/output circuit 22, output is switched from the signalsstored in the first memory 23 to the signals stored in the second memory25 (S12). For the second memory address control circuit 26, themicrocomputer 11 commands it to read the signals form the area among theareas 1 through 5 corresponding to the key operation (S13). Aftersending the audio signals of the 10-second period as output (S14),reproduction of the disk which has been reproduced is continued (S15).

When the user wants to check the contents of all disks, the useroperates the corresponding key, after which the microcomputer 11controls the memory input/output circuit 22 to switch from the signalsstored in the first memory 23 to the signals stored in the second memory25. The microcomputer 11 also commands the memory address controlcircuit 26 to read signals from the areas 1 through 5 successively. Thesignals read according to the memory address from the memory addresscontrol circuit 26 are fed to the decoder 17 via the memory datainput/output circuit 22 to restore digital audio signals. Therefore,signals of the first 10 seconds of the first music piece of each diskare successively reproduced as the audio output. In case skip ofreproduction is commanded during reproduction of the 10-second period,the microcomputer 11 commands the second memory address control circuit26 to jump to the first memory address in the area to be reproducednext, thereby enabling it to easily skip the reproduction.

Embodiment 10

FIG. 22 shows a block circuit diagram of Embodiment 10 of theinformation reproduction apparatus of the invention. Becausereproduction of partial information of all disks requires a certainlength of time, carrying out this operation every time the power isturned on forces the user to wait for a long time before reproduction isstarted. Therefore in Embodiment 10, the microcomputer 11 and the secondmemory 25 are backed up by the backup power supply 27 by utilizing thefact that the signals in the second memory 25 can be used as they are,even when the power is once shut down, if the disk is not changed. And,the changer mechanism 100 is provided with a disk detector switch 28 tosense the disk changing operation. Even when the main power (not shownin drawing) is shut down, the microcomputer 11 monitors whether or notthe disk is changed by means of the disk detection switch 28. When adisk is changed, the microcomputer 11 controls the system so that a partof information of only the new disk is reproduced after the main poweris turned on the next time. Consequently, wait time of the user, afterturning on the main power, can be eliminated when the disk is notchanged, and wait time can be reduced only when some of the disks arechanged.

The apparatus of Embodiment 10 can be applied to Embodiments 8 and 9.Although the above description assumes that the signals stored in thesecond memory 25 are those of the first 10 seconds of the first musicpiece of each disk, the signals may not be those of the first musicpiece, nor those of the first 10 seconds of any music piece, but mayinstead be those of an arbitrary period in the midst of a music piece.However, in Embodiment 8, because disk change and position search arecarried out while the signals from the second memory 25 are outputted,reproduced signals must be information of the first several seconds ofeach disk, and signals of a period of a certain length are required inorder to obtain a sufficient effect of reducing the mute period.

Although the descriptions of Embodiments 8 through 10 assume that thefirst memory 23 and the second memory 25 are separate memories, it isapparent that the similar function can be realized by controlling thememory address by the use of the same memory. Further, it is apparentthat the control function of the invention can be realized with a schemefunction other than that of the flow chart shown in FIG. 20 and FIG. 21.

As this invention may be embodied in several forms without departingfrom the spirit of the essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all of the changes that fall withinmetes and bounds of the claims or equivalence of such metes and boundsthereof, are therefore intended to be embraced by the claims.

What is claimed is:
 1. An information reproduction apparatus for readinginformation recorded on a recording medium, temporarily storing theinformation in a memory, and reading the stored information from thememory to output at a lower rate than writing information in the memory,said apparatus comprising:means for generating a write address to writeinformation read from a recording medium into memory; means forgenerating a read address to read the stored information from thememory; means for setting a first reference value specifying a lowerlimit of information amount stored in the memory; means for calculatingthe amount of stored information in the memory from a difference betweensaid write address and said read address; means for setting a secondreference value representing the upper limit of information amountstored in the memory; control means for controlling the write addressgenerating means to write the information read from the recording mediuminto the memory when the amount of stored information therein decreasesbelow the first reference value and to inhibit the writing ofinformation into the memory when the amount of stored informationexceeds the second reference value; and determining means fordetermining when a current position of the information being read fromthe recording medium reaches a predetermined position from an endposition of the information being read form the recording medium; andmeans for changing one of the first reference value and the secondreference value to increase the amount of stored information when thedetermining means indicates that the current position of the informationbeing read from the recording medium reaches the predetermined positionfrom the end position of the information being read from the recordingmedium.
 2. An information reproduction apparatus as set forth in claim1, wherein the determining means comprises:data extracting means forextracting data from the information being read from the recordingmedium which indicates an address of the end of the information on therecording medium; address determining means for determining an addressof the information currently being read from the recording medium; andmeans for comparing the address of the end of the information on therecording medium with the address of the information currently beingread from the recording medium to determine whether the current positionof the information being read from the recording medium has reached thepredetermined position from the end position of the information beingread from the recording medium.
 3. An information reproducingreproduction apparatus as set forth in claim 1, wherein the determiningmeans comprises:data extracting means for extracting data from theinformation being read from the recording means which indicates a firstamount of time which would have elapsed from a point of time beginningwhen information first recorded on the recording medium is continuouslyread from the memory means as stored information and ending when the endof the information on the recording means is read as stored information;elapsed time determining means for determining a second amount of timewhich would have elapsed from a point of time beginning when informationfirst recorded on the recording medium is continuously read from thememory as stored information and ending with the stored informationcurrently being read from the memory; and means for comparing the firstamount of time and the second amount of time to determine whether thecurrent position of the information being read from the recording mediumhas reached the predetermined position from the end position of theinformation being read from the recording medium.
 4. An informationreproduction apparatus as set forth in claim 1, wherein the changingmeans changes only the first reference value.
 5. An informationreproduction apparatus as set forth in claim 1, wherein said means forsetting the second reference value sets the second reference value as acapacity of the memory.
 6. An information reproduction apparatus forreading information recorded on a recording medium, temporarily storingthe information in a memory, and reading the stored information from thememory to output at a lower rate than writing information in the memory,said apparatus comprising:means for generating a write address to writeinformation read from a recording medium into memory; means forgenerating a read address to read the stored information from thememory; means for setting a first reference value specifying a lowerlimit of information amount stored in the memory, wherein the firstreference value setting means sets the first reference value so as totake a longer time in reading and outputting the stored information downto the lower limit amount from the memory than the mute time caused bythe disk change; means for calculating the amount of stored informationin the memory from a difference between said write address and said readaddress; means for setting a second reference value representing theupper limit of information amount to be stored in the memory; controlmeans for controlling the write address generating means to write theinformation read from the recording medium into the memory when theamount of stored information therein decreases below the first referencevalue and to inhibit the writing of information into the memory when theamount of stored information exceeds the second reference value; and,means for sequentially changing a plurality of recording media forreproducing information from the recording media.
 7. An informationreproduction apparatus for reading and outputting information from atleast one recording medium, as well as data, which is attached to theinformation and indicates a length of outputting time that theinformation has been read from the recording medium, temporarily storingthe information in a memory, and reading the stored information from thememory to output at a lower rate than the rate of writing into thememory, said apparatus comprising:means for generating a write addressto write information read from a recording medium into a memory; meansfor generating a read address to read the stored information from thememory; means for calculating the amount of stored information in thememory from a difference between said write address and said readaddress; and means for correcting the outputting time based on thecalculated amount of stored information so that the corrected outputtingtime corresponds to an outputting time of the stored information beingread from the memory.
 8. An information reproduction apparatus as setforth in claim 7, wherein the data is the recording address of theinformation on the recording medium.
 9. An information reproductionapparatus as set forth in claim 7, further comprising:display means fordisplaying the corrected outputting time.
 10. An informationreproduction apparatus for reading information recorded on a recordingmedium, comprising:reproducing means for reproducing informationrecorded on recording medium; memory means for storing said information;means for determining an amount of said information stored in saidmemory means; judging means for judging an end of said information beingreproduced from said recording medium based on a comparison of saidinformation being reproduced from said recording medium with a referencevalue; and control means for controlling the writing of said informationto said memory means such that said information is written to saidmemory means at a higher rate than said information is read from saidmemory means, said control means disabling writing of said informationto said memory means when said amount of said information stored in saidmemory means is greater than a first threshold amount and re-enablingwriting of said information to said memory means when said amount ofsaid information stored in said memory means becomes less than a secondthreshold amount, said control means stopping a reproduction process andproceeding to a next process when said judging means judges the end ofsaid information being reproduced from said recording medium.
 11. Aninformation reproduction apparatus as set forth in claim 10, whereinsaid judging means judges said end of said information being reproducedfrom said recording medium when an amplitude of said information beingreproduced from said recording medium is below a threshold level.
 12. Amethod for reading information recorded on a recording medium,temporarily storing the information in a memory, and reading the storedinformation from the memory to output at a lower rate than writinginformation in the memory, said method comprising the steps of:(a)generating a write address to write information read from a recordingmedium into memory; (b) generating a read address to read the storedinformation from the memory; (c) setting a first reference valuespecifying a lower limit of information amount stored in the memory; (d)calculating the amount of stored information in the memory from adifference between said write address and said read address; (e) settinga second reference value representing the upper limit of informationamount to be stored in the memory; (f) controlling operation of the step(a) to write the information read from the recording medium into thememory when the amount of stored information therein decreases below thefirst reference value, and inhibit the writing of information into thememory when the amount of stored information exceeds the secondreference value; and (g) determining when a current position of theinformation being read from the recording medium reaches a predeterminedposition from an end position of the information being read from therecording medium; and (h) changing one of the first reference value andthe second reference value to increase the amount of stored informationwhen the determining means indicates that the current position of theinformation being read from the recording medium reaches thepredetermined position from the end position of the information beingread from the recording medium.
 13. A method as set forth in claim 12,wherein the step (g) comprises:(g1) extracting data from the informationbeing read from the recording means which indicates an address of theend of the information on the recording medium; (g2) determining anaddress of the information currently being read from the recordingmedium; and (g3) comparing the address of the end of the information onthe recording medium with the address of the information currently beingread from the recording medium to determine whether the current positionof the information being read from the recording medium has reached thepredetermined position from the end position of the information beingread from the recording medium.
 14. A method as set forth in claim 12,wherein step (g) comprises:(g1) extracting data from the informationbeing read from the recording means which indicates a first amount oftime which would have elapsed from a point of time beginning wheninformation first recorded on the recording medium is continuously readfrom the memory means as stored information and ending when the end ofthe information on the recording means is read as stored information;(g2) determining a second amount of time which would have elapsed from apoint of time beginning when information first recorded on the recordingmedium is continuously read from the memory as stored information andending with the stored information currently being read from the memory;and (g3) comparing the first amount of time and the second amount oftime to determine whether the current position of the information beingread from the recording medium has reached the predetermined positionfrom the end position of the information being read from the recordingmedium.
 15. A method as set forth in claim 12, wherein the step (h)changes only the first reference value.
 16. A method as set forth inclaim 12, wherein the step (e) sets the second reference value as acapacity of the memory.
 17. An information reproduction method forreading and outputting information from at least one recording medium,as well as data, which is attached to the information and indicates alength of outputting time that the information has been read from therecording medium, temporarily storing the information in a memory, andreading the stored information from the memory to output at a lower ratethan the rate of writing into the memory, said method comprising thesteps of:(a) generating a write address to write information read from arecording medium into a memory; (b) generating a read address to readthe stored information from the memory; (c) calculating the amount ofstored information in the memory from a difference between said writeaddress and said read address; and (d) correcting the outputting timebased on the calculated amount of stored information so that thecorrected outputting time corresponds to an outputting time of thestored information being read from the memory.
 18. A method as set forthin claim 17, further comprising:(e) displaying the corrected outputtingtime.
 19. A method as set forth in claim 17, wherein the data is therecording address of the information on the recording medium.
 20. Aninformation reproduction method for reading information recorded on arecording medium comprising the following steps:(a) reproducinginformation recorded on recording medium; (b) determining an amount ofsaid information stored in a memory; (c) judging an end of saidinformation being reproduced from said recording medium based on acomparison of said information being reproduced from said recordingmedium with a reference value; (d) controlling the writing of saidinformation to said memory such that said information is written to saidmemory at a higher rate than said information is to be read from saidmemory; (e) disabling writing of said information to said memory when anamount of said information stored in said memory is greater than a firstthreshold amount; (f) re-enabling writing of said information to saidmemory when said amount of said information stored in said memorybecomes less than a second threshold amount; and (g) stopping areproduction process and proceeding to a next step when the step (c)judges the end of said information being reproduced from said recordingmedium.
 21. A method as set forth in claim 20, wherein said step (c)judges said end of said information being reproduced from said recordingmedium when an amplitude of said information being reproduced from saidrecording medium is below a threshold level.
 22. An informationreproduction method for reading information recorded on a recordingmedium, temporarily storing the information in a memory, and reading thestored information from the memory to output at a lower rate thanwriting information in the memory, said apparatus comprising:(a)generating a write address to write information read from a recordingmedium into memory; (b) generating a read address to read the storedinformation from the memory; (c) setting a first reference valuespecifying a lower limit of information amount stored in the memory,wherein the first reference value setting means sets the first referencevalue so as to take a longer time in reading and outputting thestoredinformation down to the lower limit amount from the memory thanthe mute time caused by the disk change; (d) calculating the amount ofstored information in the memory from a difference between said writeaddress and said read address; (e) setting a second reference valuerepresenting the upper limit of information amount to be stored in thememory; (f) controlling the step (a) to write the information read fromthe recording medium into the memory when the amount of storedinformation therein decreases below the first reference value and toinhibit the writing of information into the memory when the amount ofstored information exceeds the second reference value; and (g)sequentially changing a plurality of recording media for reproducinginformation from the recording media.